Paid Back in Full
by Taliya
Summary: Edogawa Conan, known only to a few as the shrunken Kudou Shinichi, is blackmailed into helping Kaitou KID with whatever plans he has in play. While Conan does so with his identity at stake, no one had mentioned anything against doing his utmost to annoy the living daylights out of a certain thief in the process… Rated for mild language. Written for Poirot Café's Prompt Exchange #8.


Detective Conan and Magic Kaito characters, settings, and ideas do not belong to me but to Aoyama Gōshō.

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Warnings: Mild language, spoilers for the Mystery Train arc and Movie 14: _The Lost Ship in the Sky_

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Paid Back in Full

By Taliya

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Prompt: Shinichi/Conan is the one who gets on Kaito's nerves for once. (No romance, just friendship please.)

Word Count: 4021

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The number had been simply listed as "Unknown"—that in itself was already suspicious, since it meant the caller had no desire to be traced. That it was ringing on his "Shinichi" phone was even more so, since he had changed his number almost immediately after being poisoned to make his death seem more "real" to the members of the Organization. There were only a handful of people who had this number, and he had long since changed the device's settings to automatically reject telemarketing calls.

He cautiously picked up the phone, using his voice-changing bowtie to speak in his older voice. "Hello?"

 _"Good evening, Tantei-kun,"_ trilled a voice.

He started, straightening with a blink of recognition before his eyes narrowed in concentration. "Kaitou KID-san," he greeted cautiously in reply. It was no surprise that the thief was in possession of this number, considering he had loaned the device to him during the run in with members of the Organization on the Mystery Train. "This is a first."

 _"Indeed it is,"_ he hummed. _"I'm contacting you to call in a favor."_

"A favor?" Shinichi echoed incredulously. "What favor do I owe _you_ of all people?"

 _"Oh, you know…"_ the thief said in a singsong voice that hinted of things that were not likely to be in Shinichi's favor, _"That favor you owe me for nearly dying in place of your friend, who I was disguised as."_

Shinichi gaped. "I don't owe you a favor for that. I… I let you go!"

 _"'Let me go'?"_ the gentleman thief parroted with an incredulous laugh. _"Meitantei, even if you had not 'let me go', as you say, I would have escaped from you all the same."_

"So then there's no favor to call, if you would have escaped anyway," the shrunken detective snapped back with a scowl. KID's words held the weight of truth from their multiple past confrontations, and it irked him tremendously.

KID sighed noisily. _"Oh dear,"_ he lamented melodramatically, _"I had hoped it would not come to this."_

Shinichi tensed, feeling dread curl in his gut. "Come to what?" he warily asked.

 _"Whatever would the lovely Ran-chan do if she somehow found out that her best friend, Kudou Shinichi, had been living under the same roof as her for the past year?"_ Shinichi's blood froze upon hearing the magician's threat. KID continued, his voice mockingly, whimsically mournful, _"And disguised as her adopted younger brother, no less?"_

"Don't address Ran so familiarly!" he snarled instinctively, the thief's almost kiss with his love interest three months ago still causing acid to bubble in his gut at the mere mention. "And you wouldn't _dare_ …"

 _"Oh?"_ KID crooned, his tone velvety and dark with mildly sadistic satisfaction. _"Wouldn't I?"_

"I—" Shinichi stuttered, shocked. "You—"

 _"One o'clock this Saturday at the Beika Museum,"_ KID purred, interrupting Shinichi's sputtering. _"You're going to be my younger brother. Plan to be out until the next morning."_

 _That_ stalled his brain for a moment before the realization hit. "You—You're going to use me to case a _heist location_?!" he practically shrieked.

KID hummed contentedly, neither confirming nor denying Shinichi's accusation. _"Consider this recompense for that little stunt you asked of me to perform on the Mystery Train—I believe we'll be even after this."_

"Like _hell_ we are!" the detective exploded indignantly. "You're coercing me into becoming an _accessory_!"

 _"Ah, but just think of your precious Ran-chan. We wouldn't want to anger her now, would we?"_ the magician whispered patronizingly, his voice thick with gratification that he had the upper hand and knew it.

"I _hate_ you, KID," Shinichi hissed venomously, "I really do."

 _"And I love you too,"_ KID simpered back. _"Call me back on this number by hitting redial if you need to contact me. See you Saturday, Meitantei."_

The line disconnected, and a seventeen-turned-seven-year-old Kudou Shinichi was left staring at his phone, fuming. _I cannot_ believe _—the_ nerve _of him!_ The shrunken detective gnashed his teeth in fury. _He's holding my identity hostage!_

Luckily for Shinichi, it was a Thursday evening. Ran had karate club practice after school on Thursdays, and Kogoro happened to be out—Shinichi was willing to bet the man was planted before a pachinko machine.

"So… Saturday, one o'clock at the Beika Museum," he muttered to himself. His blue eyes lit up and a smirk full of mischievous vindictiveness curled his lips as an idea came to him. "I'll see you there, KID."

He dialed the number of Agasa, waiting until the professor answered before he said, "Hakase, I'm going to need you to make something for me…"

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The museum was crowded that Saturday afternoon—exceptionally so, for a new exhibit had opened up that morning. Shinichi stopped at the edge of the museum's plaza and cast his gaze about, searching for the elusive phantom thief as he pulled out his phone and redialed the number KID had called him from—which, to his immense ire, retained its "Unknown" status despite clearly having a working number attached to it. An annoyingly too cheery, _"Hello, Meitantei!"_ greeted him, and he barely refrained from outright grimacing.

"I'm here," he replied tersely as he continued to scan the crowd. "Where are you?"

 _"By the southern wall. Blue cap, black tee, khaki pants."_ Shinichi located the aforementioned side of the building and began weaving through the throng of people. Picking out the faces of those parked against the brick, he spotted KID leaning against the wall: hair dyed several shades darker and somewhat tamed, blue eyes, and a few prosthetics on his face that changed the angle of his cheeks and the cut of his jaw. He was still similar enough to a teenaged Kudou Shinichi in appearance so as to be recognizable—still similar enough in looks to pass as the shrunken sleuth's older brother. "Fancy meeting you here," KID said in lieu of greeting as he slid his phone into a pocket with a smirk on his face.

"What are you planning?" Shinichi demanded, eyes narrowing in suspicion as he took in KID's comparatively light disguise.

KID grinned. "As I said before, you're going to pretend to be my younger brother for the day—though that's a bit ironic, isn't it?" He chuckled at the inside joke but pouted when Shinichi did not join in. The detective was still rather annoyed with the thief.

Shinichi felt a skeptical eyebrow ratchet upwards at KID's flippant behavior. "And what will we be _doing_?"

"Errands!" the gentleman thief chirped, and frankly, that was the absolute _last_ thing that Shinichi expected KID to say. He blinked in befuddlement, and KID chortled.

Confusion and irritation warred within him, and he closed he eyes as he took a deep, fortifying breath. "Let me get this straight," he stated, giving KID a piercing stare. "You blackmailed me into coming today just so you could run _errands_?"

"Bingo!" KID cheered, and this the thief time openly laughed as the detective face-palmed.

 _I cannot_ believe _I am stuck with this idiot until tomorrow!_ Shinichi thought with a mental groan. Outwardly, he only asked, _"Why?"_

The phantom thief peered down at his companion for the foreseeable future. "Isn't it more pleasant to run errands when you have someone to talk to?" to which Shinichi actually gave a strangled groan in reply. "Well, off we go," KID announced, plucking the glasses off Shinichi's face as he swept by and tucking it into his breast pocket.

"Oi! Give those back!" Shinichi snapped, making a grab for his frames.

"Disguises, Meitantei," the thief chided. He swiveled and bent at the waist so that he and the detective were nearly nose-to-nose. "Just for today, I'm going to address you by your true first name, since we're supposed to be brothers, after all—ne, _Shin-chan_?"

The detective scowled at the nickname—coming from his mother was bad enough, but KID too? Better not to let the magician know just how much he disliked the moniker. "And how am I to address you?"

"Kaito will do," he answered, and Shinichi wondered if he was addressing the thief as a variation of the word, "Kaitou". "Now," KID—Kaito—announced as he straightened and swiftly grabbed his younger brother's hand with a surprisingly gentle carefulness despite the rough appearance, "Onwards to Ueno!" He bumped into many people trying to get out of the museum plaza, sometimes even having to shoulder his way to get past the growing, winding line into the museum.

KID led Shinichi by the hand to Beika Station, even going so far as to pay for both their fares—though Shinichi had initially protested. KID had simply grinned that infuriating grin of his and said, "It's what older brothers are supposed to do, right, Shin-chan?"

Shinichi had stared, dumbfounded, for a moment before he smiled a smile that was entirely too sweet to be innocent and chirped, "Of course, Kai-nii-chan!" They boarded the train, sitting side by side with Shinichi in the seat closer to the window. As the train periodically started and stopped at various stations, he purposely squirmed, complained, and remarked on various things that he saw.

"That building over there looks sad. Why is it sad?"

"Why are only birds and bugs allowed to fly?"

"Ne, Kai-nii-chan… why does that guy over the smell so bad?"

Shinichi was able to pull of the inquisitive little kid act because he still—much to his frustration—looked like someone who was five or six, instead of seven going on eight. Well, capitalizing on his particularly youthful appearance now was going to help him with his plan of annoying the pants off of Kaitou KID. It was his version of payback for the coercion, after all.

Shinichi fired off question after question, all of them delivered with the artless truthfulness that was characteristic of young children. He was therefore quite gratified that by the time they reached the station in Shibuya there was a tightness around the thief's eyes that had not been there before. During the trip, KID had needed to apologize four times to four separate people for Shinichi's prodding questions and frank remarks regarding the appearance of other passengers on the train—or more specifically, their hygiene habits and lack thereof.

The two disembarked, one much more cheerful than the other. "Gods above, you are annoying," KID had muttered once they made it out of the station.

Shinichi grinned as he twittered, sugary-sweet, in reply, "But that's why you love me, right, Kai-nii-chan?" The phantom thief had gagged in response.

KID guided Shinichi to Ameyoko, where the thief not so gently nudged his fake younger brother into Nakata Shoten before beginning to browse through the racks of military-styled clothing. Shinichi had given him five minutes before he began whining. "Kai-nii-chan, I'm bored."

"You don't want any clothes to play dress up in, Shin-chan?" KID asked with an air of distraction as he compared two jackets.

Shinichi glared balefully at his supposed older brother. "I don't 'play' at being a member of the police, and these clothes are too big for me." He glanced about, eyes settling on a skirt before he chirped, "I'd bet you would look good in this, Kai-nii-chan!" He pattered over to the item in question and waved it, the skirt's hanger clanging against the rack.

KID gaped. "Why ever would I look good in a _skirt_ , Shin-chan?" he replied in dismay.

The detective adopted an expression of puzzlement. "But I thought you liked wearing ski—" The rest of his remark was cut off as the magician swooped down and muffled him with a hand.

The few customers in the shop, along with the store's proprietor and two employees, stared. "Kids," the gentleman thief commented with exasperation as Shinichi struggled to remove KID's hand. "You know how they ca—eww, you _licked_ me!" KID yelped, immediately releasing Shinichi and wiping his palm on his trousers. "Shin-chan!"

"You wouldn't let go," Shinichi petulantly replied, then gagged, his tongue sticking out in a universal expression of disgust. "I can't believe I did that," he muttered under his breath.

"Disgusting little brat," KID grumbled. He clasped Shinichi by the shoulders and steered him towards a chair by the changing area. "You sit here and be good," KID instructed. "I'll be back soon."

Shinichi swung his legs, giving it a minute before he hopped off the seat and ambled back towards the magician. "I'm hungry," he complained with partial honesty. While he _had_ eaten lunch before he had met with the phantom thief, Shinichi could stand to nibble on a mid-afternoon snack. It was not an unreasonable request, considering it was now nearing three in the afternoon.

"Hang on, Shin-chan," KID mumbled, studying one button up in particular.

Shinichi tugged on the thief's pant leg. "But I want to eat _now_ ," he protested, and as if to emphasize his need, his stomach gave a loud, if unintentional, gurgle.

The thief stared down his nose at the detective, clearly unimpressed. "But we ate right before we came, _didn't we?_ " he stressed, trying to force Shinichi give an answer that was favorable to the magician.

"I'm still hungry now." The shrunken detective glared up at his false older brother with a pout. "I want cake."

KID sighed noisily, tension settling in the lines of his shoulders and neck. "Shin-chan," he stated with forced patience, "Can't you wait until after I'm done looking?"

Shinichi released a loud groan, uncaring of the fact that they were beginning to attract attention once more. "But I'm so hungry! Kai-nii-chan…" he whined, drawing out the false name while insistently nudging the thief's leg.

 _"Fine,"_ KID relented, looking mildly but visibly peeved at having his shopping session cut short.

"Yay!" Shinichi cheered, throwing his hands up in the air. "Cake!"

KID leaned down, grasping Shinichi's shoulder and whispered in his ear, "I'm going to make you pay me back for that."

Shinichi twisted to stare at his older brother's face with a cute frown that morphed into a challenging smirk as he replied with saccharine sweetness, "But aren't older brothers supposed to provide for their younger brothers?"

"Little piece of—" KID hissed under his breath, though he cut himself off upon catching the disapproving stare of a woman nearby. The thief grabbed the detective's hand and almost bodily dragged Shinichi out of Nakata Shoten. They walked down the streets, turning a few corners before coming to a stop before Tsubakiya Coffee Shop. KID glanced down at the younger boy. "They have good chiffon cake here—is this what you're thinking about?"

The detective had lost KID's question, having simply latched onto the fact that the thief had brought him to a _coffee shop_. While he had not been much of a coffee drinker as his older self, Shinichi could appreciate the rich complexity of a finely brewed cup. And ever since he had become Conan, he had not had the chance to savor a cup—Ran adamantly refused to buy the drink for him.

 _Oh, gods yes!_ Without a word, he simply hauled a startled KID towards the entrance, planting the two of them at the end of the line to order. Shinichi studied at the menu written in cutesy script on an overhead chalkboard, debating what type of coffee and food he wanted.

"Do you know what you want?" KID asked, crouching down so that he did not have to speak louder than necessary in the stately but warm café filled with people enjoying a cup and reading or quietly chatting.

"Could I get the cake set: a cup of the Tsubakiya blend and a lemon chiffon cake?" Shinichi asked, pointing to the special that advertised a drink and cake combination.

KID stared dubiously at the menu. "Won't it look weird for an apparent six year old to be ordering coffee?"

Shinichi scowled at the magician. "I haven't had a good cup of java since I became like _this_ ," he quietly hissed as he gestured to his current form, "since Ran won't buy me coffee."

"All right," KID acceded with a chuckle, "I'll get you your caffeine fix. Go find us a table, yeah?"

The shrunken detective scampered off, eagerly awaiting his drink. He decided that since the thief was getting him a much desired cup of coffee, he supposed he could lay off the annoying little brother act for the duration of their time in the coffee shop. There was no need to spoil the café's pleasant atmosphere. KID returned shortly with a tray bearing their orders: a steaming black coffee and a slice of yellow cake for Shinichi, and a café latte and a slice of tea chiffon cake for the thief.

They murmured their thanks before partaking, each savoring the warmth of their respective beverages and the fluffiness of their cakes—though Shinichi drank his after he had added sugar and cream to his. As they ate and drank, they conversed over various topics, though neither of them strayed anywhere near topics broaching their personal lives. Once they were done with eating the cakes, KID disposed of their garbage and they strolled down the streets of Ameyoko, each clutching their drinks in their free hand—the other hand was clasped in each other's so as not to get lost in the crowd. Once they were done with their drinks, they disposed of the cups and continued walking.

The sun began to sink towards the horizon and the crowds began to thin when Shinichi remarked, "You're tailing someone, aren't you?"

KID immediately came to a stop, glancing down at his apparent younger brother before hurriedly hauling him off to a side street. "And what of it?" he asked softly, his tone serious.

"You should have told me earlier," Shinichi berated, "Then I would not have been so annoying."

The thief rolled his eyes. "Had you not acted as annoying as you did earlier, you might have blown my cover that much sooner," KID replied. "When did you notice?"

"On the train," the detective promptly replied. "You kept glancing at this guy in the next carriage over, though you were discrete about it. Long dark jacket, handlebar mustache? Who is he?"

"No one you need concern yourself with," the thief replied with an easy grin.

Shinichi frowned, but decided not to push. "Do we need to continue this act?"

KID nodded. "For a little while longer, I think. I just need to confirm where he is headed, and then we're done."

The detective nodded, then wordlessly grabbed the thief's hand, leading them back out onto the streets. Shinichi easily caught sight of the man that was the magician's target, and led his older brother in that direction. "Ooh, candy! Can we get some, Kai-nii-chan?" he asked as he slipped a hand into his pocket and grasped one of several small items inside.

The thief sighed heavily in exasperation. "But I just got you cake, Shin-chan! I've already spoiled your appetite enough for dinner. Kaa-san'll be upset if I get you candy too!"

"Kai-nii-chan's so mean!" Shinichi cried and broke free of KID's grasp, purposely angling towards the man and bumping him. He intentionally tripped right before he crashed into the man's legs, slipping the tracker into the cuff of one of the man's pant legs and tumbling head over foot to a stop. "Oww!" he howled, and this time he had no need to fake it—the tumble really _had_ hurt.

"Shin-chan!" KID darted through the crowd and knelt by him, making shushing noises as his eyes catalogued Shinichi's acquired injuries.

"Watch where you're going, kid," the gruff voice of KID's target snapped in irritation.

The undercover pair watched as the man stalked off before KID continued his visual check over Shinichi in the increasingly poor light. "Up you get," KID murmured, helping Shinichi stand after bandaging a particularly bad scrape on one knee. Shinichi hissed as the movement pulled on the damaged skin, but squeezed the thief's hand in thanks.

"Kai-nii-chan," he whispered, and KID bent down to hear him better. "We don't need to track him anymore." KID turned quizzical eyes upon him, and Shinichi smirked as he grabbed his glasses from KID's pocket and turned on the tracking aspect. "It's safer this way."

"But won't he find the tracker you've placed on him?" KID asked, clearly concerned about Shinichi's rather forceful involvement in affairs that were entirely not his own.

The detective shook his head. "I had a friend of mine make trackers that self destruct after a hour. They simply decompose into metallic dust with no combustion or any other noticeable reaction." He smirked at the thief's dumbfounded expression. "We're good."

"I—thank you," KID murmured, blindsided by his rival's rather thoughtful gesture.

"He looked dangerous enough to require tracking anyway," Shinichi remarked. The guy _did_ remind him of various members of the Organization, though he refrained from telling that little tidbit of information to KID. "I'd say we hang around here and get some dinner. Ramen sound good to you?"

KID smiled—a genuine smile with appreciative warmth. "Ramen sounds great."

"You're still paying, right?" he asked, and the thief's smile slid off his face. "Since for the moment you're still my Kai-nii-chan?"

The magician growled. " _Why_ do I even bother?" KID griped even as he grasped Shinichi by the hand and led them to a street side stall. They ordered ramen—with KID paying for the meal—and Shinichi traced the man's location all the way to Kabuchiko. Shinichi rattled off the address of the man's location to KID, and once the thief had written it down he sighed. "I guess I don't need to keep you out for the rest of the night," he remarked as the two of them walked towards Ueno Station.

"Why _did_ you request that I be out for the entire night?" He gave KID a sideways stare. "You weren't planning on doing any of _that_ with me, were you?" he asked suspiciously.

"What? No!" KID yelped, flailing a little. "I'm no pedophile, and I'm not into men, thank you very much!" He huffed with an indignant, injured air, his flushed cheeks visible even in the dim illumination of the streetlights.

Shinichi chuckled. "That's a relief," he teased. "I wasn't sure how well Ran would take it if she knew that my virginity had been stolen by Kaitou KID, of all people."

"She'd kill me, that's for sure," KID muttered with a shudder. They made their way inside the station after the thief paid for both of their fares—to Shinichi's bewilderment, because was their arrangement not over now that the magician had the location of his man? "My last little gesture of thanks for being such a good sport about the whole thing," KID said by way of explanation when Shinichi had asked. "It would have been a bit more difficult had you not been there—who would think of someone tailing another if there was a child sibling in tow?"

"Point," Shinichi had acceded. As the detective's train would depart earlier than the thief's, KID opted to wait with the detective on his platform.

"Thanks again, Tantei-kun," he murmured just loud enough to be heard over the approaching train. "I don't think it would have gone nearly as smoothly without you there."

"I have no idea what you are up to, KID, but just…" Shinichi gazed into KID's false blue eyes. "Be careful."

"Back at you, Kudou," KID replied with solemnity before he grinned. "I'll see you at the next heist."

Shinichi rolled his eyes as he turned and made his way for the now open train doors. "I'll make sure I catch you at the next heist," he called back, and above the hubbub of the station, he heard KID's laughter echoing throughout the platform just before the train doors shut with a mechanical hiss. Shinichi grabbed a seat, shaking his head as he muttered fondly, "Barou."

Now, how to wheedle information about the Organization's other activities from Haibara—he had to see if there was any connection to Them and KID, after all…

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Author's Note: I found this prompt to be a little harder to write than expected, though it is something that should have been right up my alley. The hardest part I had was figuring out ways for Shinichi to annoy the crap out of Kaito, since there are not many scenarios like that for me to use as a reference. Hopefully it worked out—and I am sorry if it did not tickle a funny bone or two. Not sure when coffee and chocolate addictions became a thing for Shinichi and Kaito respectively, since nowhere in the anime is there a mention of either of the two having a preference to the foods—to my knowledge. And also, I have no idea why Kaito felt the need to tail Snake—his reasons are apparently his own, but it was good enough for me to write a fic around the idea. Ameyoko is a neighborhood in Ueno that is famous for their shopping—you apparently can still haggle on prices here. Tsubakiya is an actual coffee shop in Ueno that I based Kaito and Shinichi's experience off of—the internet is a beautiful thing. Kabuchiko is a large red-light district in Shinjuku that has a lot of gang activity in addition to the prostitution. To whoever it was I wrote this for, I hope you enjoyed it.

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Completed: 19.03.2017


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